Showing papers on "B vitamins published in 1974"

Formation of the C3-Cleaving Properdin Enzyme on Zymosan Demonstration That Factor D Is Replaceable by Proteolytic Enzymes

Abstract: During incubation of ZXd2, an insoluble intermediate of the properdin system, with properdin factors D and B a complex forms, designated ZX, which cleaves purified C3. Factor D is replaceable in this system by proteolytic enzymes, e.g., trypsin, pronase or plasmin. ZX formation with ZXd2, factor B and factor D or trypsin requires the presence of Mg++. ZX complexes formed either with factor D or with trypsin are identical with respect to their stability in the absence of divalent cations and with respect to the decay of the C3-cleaving enzymes. From the data obtained with proteolytic enzymes it is concluded that factor D acts as a protease in the formation of ZX. Sequential studies of ZX formation revealed that factor B binds reversibly to ZXd2 in the presence of Mg++. The resulting ZXd2 B complex was found to acquire enzymatic activity against C3 after treatment with factor D or trypsin. Our data suggest that in the ZXd2 system two steps are involved in ZX formation, namely binding of factor B to a receptor on ZXd2, probably C3b, which occurs only in the presence of Mg++, and subsequent proteolytic activation of this complex which is Mg++-independent.

Field desorption mass spectrometry of the B vitamins: pyridoxal, pyridoxamine, their phosphates, and thiamine.

Abstract: Characterization of the B vitamins. pyridoxal, pyridoxamine, their phosphates and thiamine salts by electron impact mass spectrometry is difficult. A new technique, field desorption, is applied in ionizing these molecules for mass spectrometric analysis Characterization of these compounds by field desorption has the advantage that in each case the most intense peak in the spectrum is formed without fragmentation.

Nutritional and compositional changes in dehydro-irradiated shrimp

Abstract: Nutritional and compositional changes in dehydro-irradiated shrimp have been studied and compared with those in samples processed by conventional procedures. No changes in proximate constituents are observed due to radiation treatment, though blanching causes some loss in total proteins. Losses in B vitamins due to radiation are much less than those due to blanching and partial drying. Radiation-induced losses can be minimized by packing the samples in vacuum or nitrogen atmosphere prior to irradiation. A progressive loss up to 22% of B vitamins is observed in processed shrimp during 3 months storage at ambient temperature. No losses in total amino acids or in available lysine are observed in irradiated samples, while thermal treatment results in some losses. In vitro enzymic digestibility of shrimp protein is increased by radiation treatment.

Effect of Dietary Vitamin B Level on Fat Storage, Adipose Tissue Cellularity and Energy Expenditure in Rats and Mice Fed a High-Fat Diet

Abstract: Obesity was produced in mice and rats with high-fat diets containing various vitamin B levels (thiamin, riboflavin, pyridoxine, Ca-pantothenate, and niacin). Enlargement of fat depots, when compared w

Absorption of water-soluble vitamins.

Abstract: An account of the absorption of water-soluble vitamins must deal with the intestinal transport of a group of structurally unrelated compounds with widely different properties. The characteristics of absorption of several members of the group have not yet been adequately investigated. It is therefore difficult to make many valid generalizations. Some authors have expressed the opinion that B vitamins other than vitamin B1 2 and folic acid are absorbed by diffusion [1, 2]. According to current views on intestinal absorption, however, it seems unlikely that molecules as large as those of most water-soluble vitamins could be absorbed on any substantial scale by simple diffusion through aqueous pores. In addition, the molecules of some members of the group are fairly strongly basic or acidic. Consequently, it would be expected that a carrier mechanism would be involved in absorption in most instances, and ideological considerations might suggest that transport would be active. Only a few. years ago, there was insufficient evidence to indicate the mode of absorption of most water-soluble vitamins [3], but observations suggesting the existence of a special absorptive mechanism are now available for six of nine water-soluble vitamins, and in four cases, it is reasonably certain that intestinal transport is active in at least one mammalian species. Thus the thesis that most of these vitamins are absorbed by ‘diffusion’ is no longer tenable. Some of the main characteristics of absorption of the water-soluble vitamins are summarized in Table 17.1.

Multipath Environment Evaluation.

Abstract: : This report describes an experimental program aimed at evaluating the multipath environment typical of that which will challenge C-band microwave landing systems. The report describes the ground and air testing conducted in the Area B complex of Wright-Patterson Air Force Base, Ohio, and includes a wealth of data gathered with the aid of MLS hardware used on the prior phase of this program. A substantial fraction of the effort was devoted to measurements made on a large reflecting screen used by FAA in the test phase of Phase II of the National Landing Plan. It is concluded from the data gathered at Wright-Patterson AFB, that multipath signals generated by the use of the screen in isolation (as at NAFEC and Wallops) are quite dissimilar to those observed from real-life structures in their spatial characteristics. It is further concluded that typical hangars have quite similar reflection characteristics, almost independent of their constructional details.